Antenna system



Aug. 16, 1949. G. w. FYLEFg 2,479,331

' ANTENNA SYSTEM Filed Oct. 16, 1945 2 Sheets-Sheet 1 Invent or GeorgeW. Fyl

H is Attorney.

Aug. 16 1949. w FYLER 2,479,337

I ANTENNA SYSTEM Filed Oct. 16, 1945 2 Sheets-Sheet 2 Invehtor:

hzm 45m H is Attorn ey.

Patented Aug. 16, 1949 George W. QFyIerJStratfond, Conn .as's ignor .toGeneral ,Electric Company, a corporation of New York Application center'16, 1945, S er i'al naqesas'ia My present invention *relates 'to' highfrequency antenna systems, and particularly to high frequency Tantennasystems 1 designed to provide substantiallyfcircular radiation patterns.This application isc a continuation "in part of my U. S. Patent-No;2,405,123, granted August 6,4946. .In broadcasting radio programs withinthe higher frequency channels utilized for frequency modulation andtelevision broadcasts, it is generally desirable to :distribute theenergy radiated from the transmitting antenna as uniformly as possibleall lioiizontardirections. At the same time, it is desirable toconcentrate the radiated energy at lowrang-les in'the verticalgplane. Inother Words, iorimostefleotive service, the radiatnag-system shouldh'avea highrdegree of vertical directivity and the horizontalfield-strength patterm should be *as nearly circtilar' as possible.

Accordingly, it is an'ob'ilect of my invention to provide an improvedhigh, frequency antenna which possesses these and nth'er desirableelectrical characteristics.

In general, simple two-terminal antennas, such as dipoles theretoforecommonly used, have nonuniform radiation characteristics. It hasheretofore been customary to resort; to compound antenna arrangements inorder to secure a reasonably uniform horizontal wave pattern withhorizontal polarization. It isanother object of my invention to providean improved and simplified compound antenna structure which is capableof producing a substantially uniform radiation patten and which isrelatively'economical to build and easy to adjust.

Still another object of my invention is to provide a new and improvedantenna system which has only two connection terminals and whichnevertheless provides a substantially circular radiation pattern and theradiation of which is concehtrated substantially in the horizontalplane.

The features of 'n'iy. invention which I believe to be novel are setforth with particularity in the appended claims. My invention itself;both as to its organization and manner of operation; to-

gether with further objects and advantages thereof may best beunderstood by reference to the following description taken in connectionwith the accompanying drawing in which Fig; 1 is a perspective view ofan antenna systerii em: bodying the principles of my invention; Fig. 2shows vectorially the relationship of the current and voltage presentonthe antenna of Fig. 1;

Figst 3,- and- 5 show modifications of the system" 1 2 claims.(crash-a3) V i v.2 illustrating characteristics of antennasysteins ofthe type illustrated 'in Fig. 5; and Fig. 9shows another embodiment ofmy invention.

As is well -tinders't'o'c ic'l in the art, a properly terminatedtransmission line does not have any standing waves. In Figs- 1 and 2there iss'hown an. antenna system 'in which a transmission linesectionis utilized as aradi'ator', the 'line section being formed into'a. circular loop and the ends coupled to a suitable source bf signalvoltage. Such "an antenna has substantially uniform current and hence asubstantially circular radiation pattern in. the plane of the loop,provided proper adjustments have been made of the termination or theline and its coupling to a soiircebf high frequency waves.

In Fig. 1 there is shown such a transmission line antenna orradiatingtransmission line. The antenna comprises a substantially closedcircular loop M formed from electrically conductive material of anydesired cross-sectional shape. For example, the loop may be asuitablyformed pipe disposedwina circular configuration. The loop is coaxiallydisposed around a suitable electrically conductive member such as acylindrical grounded mast 'H to. form therewith a short section oftransmission line. l

The loop I 0 is suitably supported from the mast by means of asupporting member I 2 of insulating material, suitably connectedat itsrespective ends to, the loop and to the mast and of such length that theloop and mast are spaced apart approximately a quarter of a wavelength,or less. Thus there is provided a transmission line conductor and agrounded mast, the mast serving as a reflect'or for the loop.

There is illustrated inFigs. 1 and 2 means for energizing a system inwhich the length of the loop lilis an integral number of full wavelengths; There is provided a, transformer [3, having a primary L4 and yasecondary I5; carried by the mast H. Any suitable transmissidri line l6may be utilized to cited) the transfer of eneigy between the. primary.l4 and a suitable source of signal voltage which may comprise the highfrequency radio apparatus or transmitter represented the. box l1. One.end of the secondary I 5 is suitably connected' to the mast n and" thother terminal of the secondary is connected to the mast through avariable condenser l8. Thus winding [5 and condenser i8 constitute atuned" circuitwhich enables proper tenet transmissionnne rs; Ininstallations whr wide and operatio'r'i desired; this tuned circuit andthe anten'riasiiomdnave aibw Q: Iii s'ii'ch' a sysina'ti'on of tire;

tem, since the radiator operates as a transmission line rather than as aresonant dipole, no sharp resonance effects are present in the antenna,and the system exhibits relatively broad frequency band widthcharacteristics.

The ends of the loop ID are connected to suitable points on the coil orwinding 15 by means of suitable conductors l9 extending between the endsof the loop and the winding through a suitable opening IS in the mast.

In Fig. 2 there is shown the Vector currents flowing in the antenna IDof Fig. 1. The arrow heads on the circle IE) represent the directions ofcurrent flow within the loop and the arrows pointing inwardly from thecircle I!) represent the voltage phase relationships at the indicatedpoints. The loop I is energized from coil I by means of conductors l9connected to desired taps on winding [5. With this arrangement thereexists a difference of voltage across the ends of the and, atdiametrically opposite points of the loop, f

are 180 out of phase and may be represented by vectors pointing inopposite directions. In eifect, therefore, the currents are in phase atopposite points of the loop H], in that these currents produce additiveradiation fields along the axis of the loop, as well as radiation in allhorizontal directions.

In Fig. 3 there is depicted schematically an arrangement which enablesthe application of the above principles to a loop having an electricallength equal to an odd number of half waves. A balanced input circuit tothe loop is shown. The ends of the transmission line I6 are connecteddirectly to the ends of the loop 20, a suitable condenser being usedproperly to terminate the line in conjunction with a short length ofline joining the antenna 20 and the transmission line H5. The vectorvoltage and current relationships are shown by means of arrows. Thephase of the loop current and voltage changes uniformly andprogressively throughout the length of the transmission line antenna andthe vectors make a half revolution in approximately one half wave lengthof line. The amplitude does not change appreciably, however, and, aslong as the spacing between the loop and mast 2| is not great enough tointroduce substantial radiation resistance and, hence, attenuation, auniform substantially circular radiation pattern results.

In Fig. 4 l. have shown a modification of the antenna structure of Fig.1, in which a pair of substantially circular loop elements ID, ID eachhave an electrical length equal to an integral number of full wavelengths at the operating frequency of the antenna and, spaced from theconductive mast H by a distance equal approximately to a quarter wavelength or less, are spaced apart vertically by a distance 7\/2 equal toa half wave length. Positioned below the lower element ID by a distanceM4 equal to a quarter wave length is a conductive reflector plate H. Theends of loop H] are connected to a source of signal I! by means ofconductors l9, l6 and. the ends of loop ID are connected to the sourceby means of conductors l9, H5. The length of connection from the sourceto loop I0 is made half a wave length longer than the connection to loopl0 so that these coaxial loops carry currents which areopposite inphase. Since the currents in the loops are 180 out of phase, thehorizonta radiation of the loops is substantially completely cancelled,while their vertical radiations are additive to give a concentratedhighly directive beam of radiation. By means of the reflector l I, thisvertical radiation is confined to a single direction, namely, upwardlyalong the axis of the loops. Normal to the plane of the loop, therefore,is a concentrated beam of radiation. Such an antenna is relatively smalland simple in structure and is particularly useful where concentratedradiation in a small area is desired, for example, for betterillumination of a parabolic reflector, or for use for diathermy andtherapeutic work. Any larger even number of loops spaced apart axiallyby a distance equal to a half wave length with adjacent loops energizedin opposite phase may be used, of course, to obtain a desired strengthof radiation beam.

Fig. 5 shows the system of Fig. 3 with the addition of a drivensubstantially circular director 22 coaxially disposed and outwardlyspaced 2. fraction of a wave length from the loop 20 which in turn isspaced approximately a quarter of a wave length with respect to mast 2|by which additional vertical directivity is achieved. With thisarrangement a suitable phase delay line or matching section, indicatedby the numeral 23, is required.

Still more vertical directivity can be obtained by using stackedelements with half wave vertical spacing and excited in-phase.

In Fig. 6 there is shown a modification of my antenna system whichprovides substantially uniform current therein and, consequently, asubstantially circular radiation pattern. It is well known that a linearantenna which is actually one-half wave long at the operating frequencyhas a current distribution which is essentially sinusoidal, the currentbeing maximum at its mid-point and zero at its ends. If the antenna isless than one-half wave long and capacity is added between the ends ofthe antenna loop in an amount such that the effective electrical lengthof the entire system is equal to one-half wave, the current at the freeends of the antenna is not zero, but has some finite value and thecurrent distribution is more nearly uniform.

Accordingly, in Fig. 6, the loop or radiator 30 disposed in asubstantially closed, peripherally incomplete loop constitutes a coiledup dipole and preferably has either a length of substantially less thanone-half wave or a nearly uniform current obtained as discussed inconjunction with the description of Fig. 2. The electrical length may bemuch greater than the actual length because of the stray and, wheredesired, added capacity 3! between the ends of the loop. If the actuallength is much less than one-half wave even when the stray capacity isconsidered, the free ends of the loop may be terminated in elementsforming a condenser 3| of substantial capacity to provide a transmissionline radiator of desired length.

In order to provide the desired capacity between the ends of the loop,blocks or plates 32 may be secured, as by welding, to the ends of thepipe and U-shaped plates 33 fitted over the opposing faces of theblocks. In order to provide an adjustable condenser, one or both of theplates 33 may be provided with slots (not shown) or other suitableopenings registering with screws threaded into the blocks 32. Of course,any other desired means may be employed for varying or adjusting theeffective capacity.

A small loop does not radiate to any substantial 5 coerce is a verticaleirecti ez-y e ieee be ent ssues an e ree eris and in emcee theme- T.eere eeieq iesia e. iihich the numeral ieei'eaie e ve tical-litres...Ratta Qt e. icon-it use to obta n a reatereeeree li er-coa sitcomts withthis t me Q antenna the e be me ited a ubstantiall c cular i5 aced cctwesl item. the 1.9 it ant com mg a nlere i r o el men s es bo ine ca b e da nt nd- The rec or s su e ms con tri a ly arran ed w the ic n n d sersa n u tantial y h sam lane- The re t s p ced ae r i q the 901 a sis.-tance'bf t o f T 6 s /2 er a r i e il ap ximat l A, we e: he is t r theaso ha e a enna s stem.-

t me her-myif th spacin is too see and lit le. an i i r ct -i s bt nedif ee. is oo reat T eia h of th tor eme ts; .6 sh uld b m w a s hee 1/2ve e th so es. to i ein at l unif m. cur en di tr bution andto permitcorrect tuning. Accolxlingly, the spacing from the loop. and the lengthortl re direcel n ar n er-r lated.

a e or at nsmi si n lin or may be uti lized to, efifect transier ofenergy between he i r ue a io appa atus. r t n -n t: n p s nt by th boxstra the l op- The above ribe s stem has vertica d n e vi r Pat n a eree o by the lo es so in Fig. 6.

In Fig-,7 there is shown another modification of my antenna havingtemission line charace s e a d t e r iai r which s l en: fi d. sub a allyn. h horizo tal man there being very little radiation in the directiontransw verse om s-p s the r diat r he an there shown comprises theloopsw 4:}; whiphsure; round the mast ill. Tneloops H}, 4.1 arerelativelyclosely spaced with respect to each other and'the. 1 t s, e rm e mas i by a distance of the. order or .25. to .3 wavelengthat-thooperat: i frequency f, t stem T homes. to and. Iii-maybe supported fromthe My by insue. lat ed Supports 435, 55 to form a section of trans:mission line. surrounding the mast H.-

the same time they form a section oftl'ansn line. with most 12. Prefers.l-y, diamctc oi the, meet 5 i. the spa to the center transmis a M ii. 4?is such; the length, oi the composite line. [19, 41; is an integralnumber of half wavelengths, the number, be: cause of the physicaldimensions of the; system, being two full. wavelengths or more;

The high frequency waves from he transmitter e pp-l ed over the leadsHi. toe. resonant circuit which may comprise thestub transmis. sion lineformed of the parallel conductors 48, Q9; These conductorsv areshort-circuite and nec ed to H at one end a he H 5 and are openmlrcuitedat the. other end. The (B frqnn the transmitter are connected to thepoints 53 and the ends 5! of the loops ill jlre connected by means ofleads 5; to sym e'trically spaced points 53 on the conductors H}; and

the points 553 being displaced from the points Similarly, the ends 54 ofthe loops MI E! be connected by conductors 55 to s mmctric'all'y spacedpoints on the conductors 48, ii

The points 56, 5:3, 55 are 50 located on the transmission lineconductors Ml, 4:5 that impact-- ance matching between the componentparts or the system is obtained at, each of these points.

Thus. sierensiiee ueenthe v lta e desired t b imeresseei acro s heconduc ve oose it. 4?, the Poin s. 53 may be locat db tw nith open nd e?the con uctors 48. 5% aneithepointseel inst ad o the ocation infiiafl-Usually, however, the mints 5, a el ocateo between the points/.53 t esho t-slimmed. end of the conductor 48, 49, the d stance between the ponts-'53,. fis -3% eetermined y the voltase drop in he loops i0, 51around thcmast H. Similar-131,512: enqing upon the length of. theelements L 41, it may necessary the. transpose the conductors]! so-thatthe conductorsfl, 55 connected tocor-iductor l8, for. example, areconnected respectivelyto the-point, at on the loop It and thepoint 54'onloop 47. Such transposition. may be required for matching the phaseof. currents at the. ends or theloops k0,. Al with. currents invtheconductors 68., 4.8. In all. cases-of course/the location of the/tapsonthe transmissionline conductorsffl; Q5 is such that the desiredtermination imped ance and voltage of the connected clementsis obtained.7

In the aneratiouofi the antenna of Fig. I, the loops ll, 4?: jointlyiormasection of transmission line with respect to the grounded mast ll.'T his sectionis terminated for. reflectionlcss transmission 'of Atthesame time, the closely spaceti.loops i0, 4? form a section oftransmission line; inwhich cur-rents flaw in opposite directions,Inzavertical direction; that is, adirection parallel Withthe of the mastH, the electromagnetic field-s produced by these currents areneutralized and. cancelled sov that thereis no radiation along the axisof the mast H. However, in a hqri reenter}. direction, the fields of thecurrents in the two-loops tit, H are additive so. that the antennasystem produces radiation which is concentratedsuhstantially in a,horizontal plane. con'cluce tive. mast I l reflects energy radiatedinwardly firom. the loopathe distance between the loops iii, fland mastit being such that this energy reflected from mast" i l reinforcesenergy radiated outwardly from the loops.

In order to 'obtain still more vertical directivity in. an antenna ofthe type shewnin Fig. 6:, a plurality of assemblies may be employed,spaced. apart vertically approximately wave length. Two such assembliesare shown schematically in Fig. 9. The assemblies are interconnected inthe same phase by a suitable impedance matching line. H. A suitabletransmission. line 42. may be used to transfer energy betweentransmitter 39 and is connected. to the line. H at a pointmidway'between the assegnblies. Thedirectivity pattern for the system ofEig. 9 is represented by the lobes 43in Fig. 8.

In. :order to support the assemblies in operatime position, there may beprovided a mast ll as in Fig.6.. The loops 30 may be secured to the mastby means of members 45 of insulative material and the parasitic directorelements 36 may be supported ljrom the loop 39; by similar sup ports '46which are preferably connected to the elements 38 at points of minimumvoltage.

A plurality ofassemblies ofthe driven director type illustrated in Fig'1 may likewise be emp oyed toform a composite antenna structure forradiating greater amounts of power. Such assemblies individually have avery small amount of radiation along theaxis oif a supporting mast. Theyshould be spaced'apart ve'rtieally on 'themast, therefore, by suchdistances that: their fields in-a. horizontal direction are additivse. i

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from my invention in itsbroader aspects, and I, therefore, aim in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A high frequency antenna system comprising a substantially closedloop, a second loop spaced outwardly from said first loop to form asection of transmission line therewith terminated for refiectionlesstransmission of energy thereover, the ends of said first loopterminating in means providing substantial capacity therebetween, and atransmission line connected to said first loop on each side of saidcapacity, said first loop being sufliciently less than one-half wavelength in circumference to provide substantially uniform currenttherein.

2. A high frequency antenna system comprising a substantially closedloop, the ends of said loop being closely spaced and terminating in ameans providing substantial capacity therebetween, a transmission lineconnected to said loop on each side of said capacity, said loop beingsubstantially less than one-half wave length in circumference, anddirective means for said system comprising a plurality of separatedconductors uniformly spaced outwardly from said loop a distancesubstantially equal to one-quarter of a wave length and lyingsubstantially in the same plane therewith.

3. A high frequency antenna system comprising a substantially closedloop, the ends of said loop being closely spaced and terminating inmeans providing substantial capacity therebetween, a transmission lineconnected to said loop on each side of said capacity, said loop beingsubstantially less than one-half wave length in circumference, anddirective means for said system comprising a plurality of separatedconductors uniformly spaced outwardly from said loop a distancesubstantially equal to one-quarter of a wave length and lyingsubstantially in the same plane therewith, said conductors terminatingin means providing substantial capacity between the en-ds thereof.

4. A high frequency antenna system comprising a pair of substantiallyconcentric, substantially co-planar loops, said loops forming a sectionof transmission line terminated for substantially refiectionlesstransmission of energy thereover,

both of said loops being peripherally incomplete, and means connected toboth of said loops at the free ends thereof for supplying high frequencyenergy thereto, whereby said inner loop acts as a radiator and the outerof said loops acts as a director.

5. A high frequency antenna system comprising a vertical cylindricalconductive member, a pair of substantially concentric, substantiallycoplanar loops encircling said member, both of said loops beingperipherally incomplete, the outer of said loops being'closely spacedwith respect to the inner of said loops and the inner of said loopsbeing spaced from said member by a distance substantially equal toone-quarter of a wave, and means connected to said loops at the freeends thereof for supplying high frequency energy thereto, whereby saidinner loop acts as a radiator and the outer of said loops acts as adirector.

6. A high frequency antenna comprising a conductive mast, a pair ofsubstantially concentric, substantially co-planar conductive loopssurrounding said mast, said loops being peripherally incomplete, theinner of said loops and said mast forming a section of transmission lineterminated for reflectionless transmission of energy thereover, andmeans supplying high frequency currents to both of said loops, thecurrents in said loops having a difference in phase determined by thespacing between said loops.

7. A high frequency antenna system comprising a plurality of verticallyspaced assemblies, each of said assemblies comprising a metallicloop-like member, having a pair of ends spaced apart by a smalldistance, conductive means coupled to said respective metallic membersand concentric and co-planar therewith, a source of high frequencysignals, and means supplying high frequency currents from said source tothe respective ends of said members, said members being spaced apartvertically by an electrical distance and the phase of the currentssupplied to adjacent of said members being such the fields of saidassemblies are additive in the same direction.

8. A high frequency antenna system comprising a vertical cylindricalelectrically conductive member, a metallic loop-like membersubstantially encircling and coaxially disposed with respect to saidvertical member to form therewith a sec tion of transmission lineterminated for reflectionless transmission of energy thereover, saidmetallic member having a pair of ends spaced apart by a small distance,a source of high frequency signals, means supplying signals from saidsource to said ends, and conductive means coupled to said metallicmember and concentric and co-planar therewith for increasing thedirectivity of said system.

9. A high frequency antenna system comprising a cylindrical electricallyconductive member, a pair of concentric co-planar conductive loopscoaxially surrounding said member, said loops and said member forming asection of transmission line terminated for reflectionless transmissionof energy thereover, the outer of said loops being spaced from the innerof said loops and the inner of said loops being paced from said memberby an electrical distance substantially equal to one-quarter of the Wavelength at which said antenna operates, and means connected to said innerloop for supplying high frequency energy thereto, whereby the inner ofsaid loops acts as a radiator and the outer of said loops acts as adirector.

10. A high frequency antenna system comprising a vertical electricallyconductive member, a pair of substantially concentric, substantiallycoplanar conductive loops coaxially surrounding said member, said loopsand said member forming a section of transmission line terminated forrefiectionless transmission of energy thereover, both of said loopsbeing peripherally incomplete and having a pair of spaced ends, aresonant circuit, and means connecting said ends to spaced points insaid circuit.

11. A high frequency antenna system comprising a pair of substantiallyconcentric, substantially co-planar conductive loops coaxially spacedfrom an electrically conductive member, each of said loops beingperipherally incomplete and having a pair of spaced ends, a resonantcircuit, and means connecting corresponding ends of said loops tosymmetrically spaced points of said circuit, said loops forming asection of transmission line terminated for reflectionless transmissionoi. energy thereover.

12. A high frequency antenna system comprising an electricallyconductive member, a pair of concentric (ac-planar conductive loopscoaxially surroundin said member, each of said loops being peripherallincomplete and having a, pair of spaced ends, a section of transmissionline, means supplying high frequency waves to a first point on saidline, means connecting corresponding ends of said loops to symmetricallyspaced points on said line, the points of connection of said energy tosaid line and of said ends to said line being so spaced that highfrequency waves are transmitted from said first means to said loopssubstantially 15 without reflection.

GEORGE W. FYLER.

10 REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS

